This article proposes what it describes as a pyramid model of radicalisation, being a pyramid because the small number of people who turn to terrorist action are at the apex of a much larger group of sympathisers who share their beliefs and feelings. It might be better not to describe the ideas presented as a model as, as the authors themselves suggest in their conclusion, what they produce are a number of different pathways of radicalisation without any single underlying theory to suggest why people may take one, another, or in many cases several of the pathways to becoming radicalised.
There are three groups of pathways, individual, group and mass. By including the latter category the authors also discuss how large populations (they mention the U.S.) can also be radicalised through some of the same mechanisms as non-state ‘terror’ groups. Within these three groups of pathways the authors suggest twelve mechanisms by which people may become radicalised, although they also suggest that there could be more. Some of the mechanisms themselves are not very tightly supported, but the article in itself brings together a range of literature from psychological studies and theories by applying these in a structured fashion could be a useful introduction readers interested in what psychology can bring to explanations of radicalisation. The article is also a good example of standard theories of radicalisation of the ‘what makes a normal person come to act in abnormal ways’ type.